Self-locking stud



May 11, 1948. c. E. 5. PLACE El AL 2,441,442

SELF LOCKING STUD Filed July 26, 1946 flTTURNE Yd Patented May 11,1948

estate I g Marsha ll Van manna, Oceanport, N. J. l v

jiapplication iru'iy 'zc, 1946, Serial No. 686,416

'7 4 Claims. (Cl;

This invention relates to a self-locking stud or the like, and particularly to such a stud or machine screw which may be screwed readily into a threaded hole in the work and which will then resist removal as strongly as may be necessary.

An object of the invention is to provide such a stud in which the parts may conveniently be made on available automatic machines.

A further object is to provide such a stud in which the action of the locking part does not prevent the main threads of the stud from carrying their working load on the proper side.

Another object is to provide certain improvements in the form, construction and arrangement of the parts whereby the above named and other Y objects may effectively be attained.

A practical embodiment of the invention is represented in the accompanying drawings, in which Fig. 1 represents a section of a work-piece, taken axially of a hole drilled therein and showing in side elevation a standard tap with chamfer portion used for tapping threads in said hole;

Fig. 2 represents a corresponding section of the work-piece showing in side elevation the selflooking stud locked in the hole, and

Fig, 3 represents a transverse section, taken on the line IIIIII of Fig. 2, looking in the direction of the arrows.

Referring to the drawings, a work-piece I in which a stud is to be set is shown as having a hole 2 drilled or otherwise formed therein. Threads 3 are tapped in the hole 2, preferably by means of a standard tap 4 with a chamfer portion 4' (as distinguished from a bottoming tap) so that the lower threads have decreasing major diameters toward the bottom of the hole.

The stud 5 is provided with holding threads 6 matching and fitting the threads 3 with any convenient degree of closeness. Studs are customarily made with a close class 4 or even class 5 fit, but in the present case such expensive accuracy is not needed, and the fit may be no closer than class 2 or three. At its lower end the stud is reduced in diameter to form a cylindrical neck I on which is freely mounted an annular ferrule 8. The neck is upset to form a head 9 which retains the ferrule loosely on the neck. The matching annular end faces of the stud and ferrule are formed withradially disposed complementary clutch or ratchet teeth I0 and II, respectively, and the ferrule is provided with threads I2, of the same character as the threads 6 on the stud and so disposed as to be in phase with the latter when the teeth I0 and I I are fully engaged. i

' I he-helicaiangle ot' thezteeth lilcand filzfshoultl be greater than, and in the same direction as, the helical angle of the threads 6 and I2; and the axial motion permitted to the ferrule by the head 9 should be slightly less than the height of said teeth.

In operation, the stud is screwed into the hole.

with the threads I2 of the ferrule in phase with the threads 6 of the stud; that is, with the teeth I0 and II fully engaged. The stud may, if convenient, be screwed in to a point where the threads 12 bind against the lower threads 3 of reduced diameter, or it may be screwed in a lesser distance, as shown in Fig. 2. In either case locking is effected immediately when the stud is turned in the reverse direction, since the frictional engagement of the threads I2 on the ferrule with the threads 3 in the hole (particularly in the lower tapered part, but adequately in the straight part) causes the ferrule to lag behind the stud and thus to be driven strongly downward away from the stud by the wedging action of the clutch teeth I0 and I I. The greater the unscrewing force applied to the stud, the greater will be the downward pressure against the ferrule, while a. corresponding increase in the frictional engagement of the threads I2 with the threads 3 continuously prevents the ferrule from turning with the stud.

We contemplate bringing the threads of the stud and those of the hole into such tight frictional engagement that the common fibre insert form of locknut, or other forms having initially a relatively high friction fit, may be applied without freeing the stud.

When thus locked in position the threads 6 on the stud engage with their upper faces against the lower faces of the threads 3 and thus carry the working load on the proper side to assure rigidity and accuracy.

The surfaces of the teeth I0 and II are generated by radii perpendicular to the axis of the stud to provide the best distribution of the axial pressure during locking, and the height of said teeth is not only greater than the maximum relative axial motion permitted by the head 9 but is also greater than the maximum amount of axial play found in the loosest practicable fit between the stud and work-piece. Since the locking of the stud results from an artificial and mechanical tightening of the fit, the original tightness or looseness of the fit is unimportant and no care need be taken to meet exacting tolerances in this respect, particularly if the stud is seated at a depth such that the ferrule threads be resorted to in the form, construction and ar V rangement of the several parts without departing from the spirit and scope of my invention,

details herein shown and described, except y be included in the claims. I a 1 What we claim is: V

l. A device of the character described comprisneck portioniscylindrlcal and substantially c0- axial-with the shank, and is provided with a ing, a threaded shank, a neck portion of reduced 4 portion, the end of the shank and adjacent end of the ferrule being provided with complementary clutch teeth and the threads of the ferrule bein in phase with the threads of the shank when said teeth are fully engaged, the helical angle of the clutch teeth being greater than, and in the same direction as, the helical angle of the threads.

2. A device according to claim 1 in which the neck portion is provided with means for limitin the axial motion of the ferrule. I

3. A device according to claim 1 in which the neck portion is provided with means for limiting I the axial motion of the ferrule to a distance less and hence I do not intend to be limited to the V as theythan the height of the teeth.

4; A device according to claim 1 in which the head for; limiting the axial motion of the ferrule.

CHARLES E. S. PLAQE. MARSHALL VAN WINKLE, JR. 

